The present invention relates to diecuttable polyester urethane foams and, more particularly, to improvements in the diecuttability of such foams.
Polyester foams manufactured for use in applications requiring good diecuttability, i.e., -- the ability to be diecut or stamped to various shapes, have a history of variable diecuttability performance. Day-to-day variations in performance have consistently plagued the processing of this type of foam.
Typical problems include too slow recovery to the original height of the foam and permanent edge curl or deformation of the resulting diecut foam. Perhaps the most severe problem is caused when the edges of the diecut foam have become sealed or welded. These problems are particularly acute with lower density foams.
The magnitude of the general problem of providing satisfactorily diecuttable foams has engendered a multitude of theories as to the causes of good (or poor) diecuttability as well as techniques for improving diecuttability. Thus, to achieve improved diecuttability, it has been proposed that: lubrication of the urethane is required, the foams must be fairly open, course celled foam is better than fine celled foam, and raising the tolylene diisocyanate index aids as well as other suggestions. Many manufacturers of polyester foam for diecuttable applications employ relatively high molecular weight amine compounds as additives in an attempt to improve diecuttability. Typical of such additives include N-coco morpholine (morpholinated coconut oil) and N-lauryl morpholine.
Despite these many suggested techniques and theories, the provision of consistently satisfactory polyester foams for diecutting applications remains a problem.
While an ostensibly ready solution would be the utilization of polyether foams, which typically provide adequate diecuttability, this is not wholly satisfactory. Many and diverse specialty applications (e.g. -- hair curlers and the like) require aesthetic foam characteristics not generally available when polyether foam formulations are used. A modification in the foam formulation such as, for example, the particular isocyanate used, may provide some improvement; but this is generally unacceptable due to the associated inventory problems.
The inclusion of low combustibility additives into foam formulations for diecutting applications has further heightened the problem. The overall result is that it is estimated that somewhere in the range of about 10 to 30 percent of the polyester foam used for commercial diecutting applications must be rejected due to unsatisfactory diecuttability. The accompanying economic penalty is apparent.
It is thus an object of the present invention to provide a method of obtaining polyester urethane foams characterized by consistently improved diecuttability. A related object provides polyester urethane foams possessing improved diecuttability properties even when low combustibility additives are employed in the foam formulations.
A still further and specific object of this invention is to provide polyester urethane foams having improved diecuttability characteristics without causing any concomitant significant adverse affects on the foam characteristics.
Yet another object provides an additive formulation for diecuttable polyester foams with suitable viscosity and compatibility to allow easy handling with conventional formulations.
Another object is to provide relatively low density polyester urethane foams with improved diecuttability properties.
Other objects and advantages of the present invention will become apparent from the following detailed description.
While the invention is susceptible to various modifications and alternative forms, there will herein be described in detail the preferred embodiments. It is to be understood, however, that it is not intended to limit the invention to specific forms disclosed. On the contrary, it is intended to cover all modifications and alternative forms falling within the spirit and scope of the invention as expressed in the appended claims. Thus, while the advantageous results of the present invention are exemplified herein in connection with certain polyester foam formulations, it should be appreciated that the present invention is equally applicable to use in connection with any polyester foams possessing diecuttable properties.